1. Field of the Invention
The present invention relates to a magnetic transferring method for performing magnetic transfer from a master medium bearing information to a slave medium.
2. Description of the Related Art
The magnetic transferring method is designed to transfer a magnetic pattern corresponding to information (e.g., servo signal) borne by a master medium by applying a transfer magnetic field while the master medium bearing transfer information by the micro uneven pattern of a magnetic material and a slave medium subjected to the transfer are kept in a state of close contact. As such magnetic transferring methods, for example, there are those disclosed in Japanese Unexamined Patent Publication Nos. 63(1988)-183623, 10(1998)-40544, 10(1998)-269566, and others.
In a hard disk, a high recording density flexible disk or the like that is used as the slave medium, the surface of a magnetic recording layer has a lubricating layer formed in order to reduce friction generated by contact with a magnetic head during use.
However, during the magnetic transfer by the above-described magnetic transferring method, a problem sometimes occurs if the lubricating layer like that described above is formed on the recording plane of the slave medium. Specifically, it may be difficult to peel off the slave medium from the master medium after the magnetic transfer is performed in close contact with the master medium. In addition, dust stuck to the master medium may be adhered to the slave medium after the close contact, causing the increase of an error rate during recording and reproducing in actual use.
Analysis of the slave medium after the magnetic transfer revealed that the meniscus of the lubricating layer formed on the recording plane brought about an increase in a close contact force between the slave medium and the master medium. It was also discovered that the dust stuck to the master medium was adsorbed on the lubricating layer. Such a phenomenon was particularly conspicuous in slave mediums including a metallic thin-film magnetic recording layer.
The high close contact force between the slave medium and the master medium makes it difficult to separate the slave medium from the master medium after the magnetic transfer. Forcible peeling-off may damage the slave medium or the master medium. If there is dust adsorbed on the lubricating layer of the slave medium during the magnetic transfer, it is difficult to remove the dust in post-treatment because of strong adhesion force. Following the high-speed rotation of the slave medium, the dust may collide with the magnetic head to cause head crashing or dropout. Consequently, an error occurrence rate may be increased.
The present invention was made in view of the foregoing problems, and it is an object of the invention to provide a magnetic transferring method designed to facilitate the separation of the slave medium from the master medium after the magnetic transfer and prevent the adsorption of dust on the slave medium.
During the magnetic transfer by the above-described magnetic transferring method, the close contact state between the slave medium and the master medium affects signal quality after the magnetic transfer. Ideally, a distance between the recording plane of the slave medium and the information bearing plane of the master medium should be set to be less than or equal to 100 nm, and the close contact is required to be in a uniform state on the full surfaces thereof.
However, dust may be present between the master medium and the slave medium, and space may be formed between the master medium and the slave medium in the vicinity of the dust depending on the size of the dust, making it impossible to realize a close contact state with a uniform distance across the full surfaces. Thus, a difference is generated in the transferred magnetic signals in accordance with the above-described distance, reducing signal quality, and generating an intensity distribution in a read out reproducing output. When the recorded signal is a servo signal, the tracking function is not sufficient, reducing reliability. Regarding the dust, it was discovered that the sticking of powder dust or the like generated during the manufacturing process of the slave medium to the surface thereof was a main cause.
The present invention was made in view of the foregoing problems, and it is an object of the invention to provide a magnetic transferring method designed to improve signal quality by making the close contact distance between the slave medium and the master medium uniform during the magnetic transfer.
In addition, during the magnetic transfer by the above-described magnetic transferring method, depending on the repeated use of the master medium, the master medium may be contaminated by foreign articles stuck to its surface. The foreign articles stuck to the master medium are mainly dust, fiber flocks, and so on, generated in the surrounding environment.
If the magnetic transfer is carried out while such articles are stuck to the master medium, close contact cannot be secured between the master medium and the slave medium in an area ranging from the dust stuck portion as a center up to a periphery. Consequently, it is impossible to carry out pattern transfer at a predetermined signal level, reducing transfer quality. When the recorded signal is a servo signal, a tracking function will not be sufficient, causing a reduction in reliability.
The repeated close contact between the master medium and the slave medium increases the sticking force of the above-described articles stuck to the surface of the master medium, and equal or more pattern transfer failures occur in all the slave media subjected to the magnetic transfer thereafter. Consequently, many defective products are produced. Further, such stuck articles may deform the surface of the master medium, leading to the loss of its normal function.
To remove the articles stuck to the master medium, the master medium before the magnetic transfer may be subjected to cleaning carried out by ultrasonic washing using a cleaning solution, wiping or the like. However, by such a method, the removed articles may be adhered again to the master medium after washing, therefore providing insufficient removal and generating a water mark on the surface of the master medium when the cleaning solution is dried or rubbing damage by a wiping material. Consequently, signal transfer failures or master medium damage may occur. In other words, even if the stuck articles are temporarily removed by the cleaning solution or the wiping material, the articles may be adhered again from the cleaning solution remaining on the surface of the master medium or the wiping material. Especially, there are some fine grains which cannot be removed.
The present invention was made in view of the foregoing problems, and objects of the invention are to provide a method and an apparatus for cleaning a master medium for magnetic transfer capable of performing high quality magnetic transfer, by removing articles stuck to the master medium in a dry process and in a non-contact manner without any re-adhesion thereof.